File: bitvec.c

package info (click to toggle)
bow 19991122-4
  • links: PTS
  • area: main
  • in suites: woody
  • size: 2,544 kB
  • ctags: 2,987
  • sloc: ansic: 38,660; lisp: 1,072; makefile: 594; perl: 492; yacc: 149; sh: 91
file content (215 lines) | stat: -rw-r--r-- 5,821 bytes parent folder | download | duplicates (4)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
/* Getting and setting bits in a bit-vector. */

/* Copyright (C) 1997, 1998 Andrew McCallum

   Written by:  Andrew Kachites McCallum <mccallum@cs.cmu.edu>

   This file is part of the Bag-Of-Words Library, `libbow'.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License
   as published by the Free Software Foundation, version 2.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA */

#include <bow/libbow.h>
#include <assert.h>
#include <string.h>		/* for memset() */

#ifndef BITSPERBYTE
#define BITSPERBYTE 8
#endif

/* Allocate, initialize and return a new "bit vector" that is indexed
   by NUM_DIMENSIONS different dimensions.  The size of each dimension
   is given in DIMENSION_SIZES.  The size of the last dimension is
   used as hint for allocating initial memory for the vector, but in
   practice, higher indices for the last dimension can be used later,
   and the bit vector will grow automatically.  Initially, the bit
   vector contains all zeros. */
bow_bitvec *
bow_bitvec_new (int num_dimensions, int *dimension_sizes)
{
  bow_bitvec *ret;
  int i;
  int num_bits = 1;

  ret = bow_malloc (sizeof (bow_bitvec));
  ret->num_dimensions = num_dimensions;
  ret->dimension_sizes = bow_malloc (num_dimensions * sizeof (int));
  for (i = 0; i < num_dimensions; i++)
    {
      ret->dimension_sizes[i] = dimension_sizes[i];
      num_bits *= dimension_sizes[i];
      assert (num_bits > 0);	/* attempt to check for overflow? */
    }
  ret->vector_size = num_bits / BITSPERBYTE + 1;
  ret->vector = bow_malloc (ret->vector_size);
  bow_bitvec_set_all_to_value (ret, 0);
  return ret;
}

/* Set all the bits in the bit vector BV to 0 if value is zero, to 1
   otherwise. */
void
bow_bitvec_set_all_to_value (bow_bitvec *bv, int value)
{
  memset (bv->vector, (value ? ~0 : 0), bv->vector_size);
}

/* If VALUE is non-zero, set the bit at indices INDICES to 1,
   otherwise set it to zero.  Returns the previous value of that
   bit. */
int
bow_bitvec_set (bow_bitvec *bv, int *indices, int value)
{
  int i;
  int bit_index;
  unsigned char *vector_byte;
  int ret;

  for (i = bv->num_dimensions-2, bit_index = indices[bv->num_dimensions-1];
       i >= 0;
       i--)
    {
      bit_index = bit_index *  bv->dimension_sizes[i] + indices[i];
    }
  if (bit_index / BITSPERBYTE >= bv->vector_size)
    {
      /* The bit vector needs to grow to accomodate this entry. */
      int old_size = bv->vector_size;
      int increase = 3;

      if (bv->vector_size * increase / 2 <= bit_index / BITSPERBYTE)
	increase = 4 * bit_index / (BITSPERBYTE * bv->vector_size);
      bv->vector_size *= increase;
      bv->vector_size /= 2;
      bv->dimension_sizes[bv->num_dimensions-1] *= increase;
      bv->dimension_sizes[bv->num_dimensions-1] /= 2;
      bv->vector = bow_realloc (bv->vector, bv->vector_size);
      memset (bv->vector + old_size, 0, bv->vector_size - old_size);
    }
  vector_byte = &(bv->vector[bit_index / BITSPERBYTE]);
  ret = (((*vector_byte) & (0x80 >> (bit_index % BITSPERBYTE))) ? 1 : 0);
  if (value)
    (*vector_byte) |= (0x80 >> (bit_index % BITSPERBYTE));
  else
    (*vector_byte) &= ~(0x80 >> (bit_index % BITSPERBYTE));

  /* Update the bits_set count */
  if ((value == 0) && (ret == 1))
    bv->bits_set--;
  else if ((value != 0) && (ret == 0))
    bv->bits_set++;

  return ret;
}

/* Return the value of the bit at indicies INDICIES. */
int
bow_bitvec_value (bow_bitvec *bv, int *indices)
{
  int i;
  int bit_index;
  unsigned char vector_byte;

  for (i = bv->num_dimensions-2, bit_index = indices[bv->num_dimensions-1];
       i >= 0;
       i--)
    {
      bit_index = bit_index *  bv->dimension_sizes[i] + indices[i];
    }
  /* If this index is beyond the end of the vector, just return 0. */
  if (bit_index / BITSPERBYTE >= bv->vector_size)
    return 0;
  vector_byte = bv->vector[bit_index / BITSPERBYTE];
  return ((vector_byte & (0x80 >> (bit_index % BITSPERBYTE))) ? 1 : 0);
}

/* Free the memory held by the "bit vector" BV. */
void
bow_bitvec_free (bow_bitvec *bv)
{
  bow_free (bv->dimension_sizes);
  bow_free (bv->vector);
  bow_free (bv);
}


#if BOW_BITVEC_TEST
int main (int argc, char *argv[])
{
  bow_bitvec *bv;
  int d1 = 100;
  int d2 = 37;
  int d3 = 12;
  int numbits = d1 * d2 * d3;
  int dims[] = {d1, d2, d3};
  int ind[3];
  int i,j,k;
  int old;

  bv = bow_bitvec_new (3, dims);

  for (i = 0; i < d1; i++)
    {
      ind[0] = i;
      for (j = 0; j < d2; j++)
	{
	  ind[1] = j;
	  for (k = 0; k < d3; k++)
	    {
	      ind[2] = k;
	      old = bow_bitvec_set (bv, ind, (i+j+k)%2);
	      assert (old == 0);
	    }
	}
    }

  for (i = 0; i < d1; i++)
    {
      ind[0] = i;
      for (j = 0; j < d2; j++)
	{
	  ind[1] = j;
	  for (k = 0; k < d3+100; k++)
	    {
	      ind[2] = k;
	      old = bow_bitvec_set (bv, ind, (i+j+k)%3);
	      if (k < d3)
		assert (old == (i+j+k)%2);
	    }
	}
    }

  for (i = 0; i < d1; i++)
    {
      ind[0] = i;
      for (j = 0; j < d2; j++)
	{
	  ind[1] = j;
	  for (k = 0; k < d3+100; k++)
	    {
	      ind[2] = k;
	      old = bow_bitvec_value (bv, ind);
	      assert (old == (((i+j+k)%3) ? 1 : 0));
	    }
	}
    }
  printf ("Test succeeded.\n");
  exit (0);
}
#endif /* BOW_BITVEC_TEST */

/*
Local Variables:
compile-command: "gcc -DBOW_BITVEC_TEST bitvec.c -g -o bvt -L. -lbow"
End:
*/